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EntropyOP•

Saw this on r/rust. Still alpha quality, but looks interesting. It will take a load of disparately sized disks and create multiple arrays across them while utilizing as much space as possible. So like a 4tb + 2tb + 2tb set up disks would get 2 4tb (gross) logical drives set up, then have those glommed together with lvm thin provisioning on top, with xfs as the filesystem.

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michrech•

That sounds awfully hack-y. How does it handle a situation where you want to remove, say, a 2TB drive to replace it with a larger drive (or can it handle that)?

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EntropyOP•

I assume the worst outcome there would be some wasted space if it doesn't have an open target to stripe against. I also don't really think it's hacky - LVM does all this. It's just a pain to configure and maintain for disparately sized disks. There's also snapraid, unraid, btrfs. They all can do this sort of thing. btrfs is probably the closest to what this is trying to do, but it's limited to the btrfs filesystem, of course.

Then again, like I said, it's alpha code.

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gimpbully•

Why would you use the one fs that can't shrink for this soft of hackery...?

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EntropyOP•

Hence the LVM thin provisioning.

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gimpbully•

No, I saw that... It doesn't solve the issue at all, it just implements a low-water mark.

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EntropyOP•

You should tell this to the device mapper people so they stop wasting their time.

Snark aside, I think getting 6tb of storage out of 6tb of space (that used to be 9) without rebuilding the array qualifies for some definition of "solved".

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gimpbully•

Thin provisioning has absolute utility and it has some marginal utility here, I still just don't get why they're not using one of the many shrinkable file systems. That seems to have far broader utility than anything xfs affords.

And no, if you exceed that 6TB at ANY time in the lifetime of your file system, you simply cannot get 6TB out of that previous 9.

edit: watching their linux conf presentation really shows this is no where near fully baked yet. Their reshaping stuff is just close to done yet. And the answer to XFS, flippantly, is because it's a redhat dev. Of course they're pimping xfs.

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